1. Field of the Invention
The invention concerns a magnetic field generation device for an apparatus for magnetic resonance tomography, as well as an apparatus for magnetic resonance tomography with such a magnetic field generation device.
2. Description of the Prior Art
Magnetic resonance tomography is an imaging modality for which very high magnetic fields (up to multiple Tesla) are required. Superconducting magnetic coils are used to generate such high magnetic fields. So that the material of the magnetic coils is superconducting, it must be significantly cooled. Such a cooling typically takes place with liquid helium. The helium in conventional apparatuses for magnetic resonance tomography is located together with the magnetic coils in a cryostat. The container in which the liquid helium and the magnetic coils are located is surrounded by a thermally insulated vacuum container with a vacuum therein. If the magnetic coils transition into the normally conductive state, an event known as a quench occurs, and the energy of the magnetic field is transduced into heat. The liquid helium thereby suddenly vaporizes and expands at the transition into the gas phase. In order to avoid an explosion of the cryostat, the gas is discharged via a component known as a quench pipe. In order to avoid consequential damage (such as asphyxiation of patients and treatment personnel), the gaseous helium is discharged into a region outside of the room in which the apparatus for magnetic resonance tomography is located. The helium is thereby lost, and an expensive refilling of the cryostat with liquid helium is necessary. Furthermore, the installation of a quench pipe is complicated, and the quench pipe, or the valve installed therein, must be regularly monitored for blockage (for example by ice formation).
From DE 10 2005 042 112 B3, a device is known for monitoring a quench pipe of a superconducting magnet with a quench pipe inside of which are arranged at least one illumination unit and at least one image acquisition unit. The image acquisition unit is furthermore connected with an image presentation unit so that the state of the inside of the quench pipe can be monitored visually. Blockages (by ice, for example) can therefore be detected.